1. Field of the Invention
This invention relates to a field emission device or element and process for manufacturing the same, and more particularly to an electron emission element of the field emission type suitable for use as an electron source for various equipment such as a display element, a printer head, a light source, an amplifying element, a high-speed switching element, a sensor and the like and a method for manufacturing the same.
2. Discussion of Background
FIG. 14 shows a conventional electron emission element of the field emission type as disclosed in Japanese Patent Application Laid-Open Publication No. 33833/1989. This field emission element includes an insulating substrate 200 and an emitter 202 on the substrate 200 having a triangular projection 201 with an acute distal end at its central portion. The field emission element also includes a gate 204 which is adjacent the emitter 202 on the substrate 200 and has an opening 203 corresponding to the projection 201. A secondary electron emission electrode 205 is located on the substrate 200 opposite to the emitter 202 with the gate 204 being interposed between them and parallel to the gate 204.
In the conventional field emission element constructed as described above, the application of a predetermined potential between the emitter 202 and the gate 204, as well as between the gate 204 and the secondary electron emission electrode 205, causes electrons to be emitted from the projection 201 of the emitter 202 to pass through the opening 203 of the gate 204 and to impinge on the secondary electron emission electrode 205, resulting in the secondary electron emission electrode 205 emitting secondary electrons.
As described above, in the conventional field emitting element, the emitter 202, gate 204 and secondary electron emission electrode 205 are arranged side by side on the substrate 200. The electrodes are separately formed by means of separately prepared mask patterns. This causes the intervals between the electrodes to be set or determined in dependence upon the exposure resolution in the photolithography processing, the accuracy of the etching, the accuracy of the master patterns, the accuracy of the registration or alignment between the master patterns, and so on.
A reduction in drive voltage for the field emission element is attained by decreasing the interval between the electrodes. Unfortunately, the conventional field emission element fails to practice accurately the photolithography processing for determining the interval between the electrodes. Such a restriction in the manufacturing of the field emission element results in the interval between the electrodes in the conventional field emission device failing to be reduced uniformly with good reproducibility, which leads to a failure to decrease the drive voltage for the field emission element to the required amount.
The present invention has been made in view of the foregoing disadvantage of the prior art.